DreamCatcher

Hello all!

Since the last month or so, my Maxima has been having a rough idle. It is minor, fluctuates about ~70RPM. When I drive it around, the car worked just fine.

But now, the idling RPM issue is still there, but in addition, I have a very uneven noise coming out of the exhaust. It seems as if there are tons of airpockets in the system or something.

Here is a YouTube video of my exhaust with the uneven noise.

Also, it feels as if the car accelerates slowly between the RPM of 1K-2.5K. Once it hits over 2.5K the acceleration catches up. In other words, the acceleration is not linear, more of an exponential increase.

Can anyone please give me any suggestion on what to check? Thanks a lot! I have a manual transmission, if that makes a difference.
EDIT: The ECU has not given out any codes.

PS. Sorry, I couldn't get the George Lucas magic in my YouTube video- cell phone video cameras don't give me a lot to work with

AndrewR2442

iTrader: (1)

coil packs are probably getting old and it's time for replacement.
fuel injectors may be nasty. use some injector cleaner first.

There are two tests the home mechanic can make, the sound test and the resistance test.

Sound test...
This test is performed with the engine idling. Use a mechanic's
stethoscope or a length of rubber vacuum hose, and listen to each injector.
All injectors should sound alike. If you find one which makes a different
sound (or no sound at all) you have found a problem.

Resistance test...
This test is performed with the engine off. Use an ohmmeter to measure the
resistance of each injector. This does not require removing the injectors.
I don't know the correct resistance value for the injectors on your model,
but they are typically a low number such as 16 ohms. The important thing
is they should all be equal. If you find one injector with substantially
higher resistance than the others, it is bad. If you find one with zero
ohms (short circuit) that is truly unfortunate, because the injector is bad
and it may also have damaged the Engine Control Module (the computer)
because of excessive current drain.

Measuring the resistance of the front bank of cylinders is easy because the
injectors are in plain view. Disconnect the injector electrical connector
for cylinder #2, measure the resistance, reconnect the connector. Repeat
for the cylinders #4 and #6.

Measuring the resistance of the rear bank of cylinders is almost as easy,
but it is difficult to reach the injectors. The resistance may be measured
at a conveniently located electrical connector. Notice the largest,
thickest electrical harness at the top of the engine. This is the Engine
Control Harness and it is shaped like a U, with the open top of the U at the
driver's side of the car. The U has two corners. Look at the corner
nearest the passenger seat. Just inside that corner you will find an 8-pin
electrical connector. This is connector F131. Disconnect this
connector. Now look at the male part, the connector half with the pins
exposed. They are arranged in two rows of four pins.
The pins are numbered 1 - 4 (top row) and 5 - 8 (bottom row).
Measure the resistance of:
- injector #1 between pins 1 and 2.
- injector #3 between pins 1 and 6.
- injector #5 between pins 1 and 5.
Be sure to measure the PINS, not the female receptacles.

The dealer's shop is equipped with high-tech diagnostic instruments. These are wonderful devices but they are expensive and the dealer has to recover his cost by charging you for diagnostic time. Sometimes the home mechanic can do legitimate diagnostic work with nothing more than a ohmmeter and a rubber tube.

To Test Ignition Coils:
With the ignition off, disconnect the electrical connector from the ignition coil. Connect the positive (+) probe of an ohmmeter to terminal no. 1 and the negative (-) probe to terminal no. 2 of the coil connector - the meter should indicate infinite resistance. Reverse the meter leads ( negative probe to terminal no. 1 and positive probe to terminal no.2) - the continuity should be indicated, but not zero ohms. If the results are not as specified, replace the coil.
Connect an ohmmeter between the secondary terminal ( the one that the spark plug connects to) and terminal no. 1 - the meter should indicate infinite resistance. If not, replace the coil.
Note - Ohm meter to test coils is not the most reliable way. Some peoples’ coils tested perfectly, but they still misfired.

DreamCatcher

Thanks a lot for the detailed info.

I have used fuel injector cleaner additives in my gas tank, but they don't seem to make any difference.

If one of the coil packs were out, wouldn't this problem be there across the board- while idling, and also when the engine is under load?

Thanks again!

pmohr

iTrader: (26)

Not necessarily. Most often you'll notice a coil growing weak when stopped, under load (say, in Drive with foot on the brake).

DreamCatcher

Would there be a way to replicate that in a manual transmission vehicle, i.e. coil growing weak when stopped, but under load?

I plan on taking the vehicle to a mechanic- I am just getting a good idea of what could possibly be wrong, so that I don't look like a dumb@ss when I am talking to him!

Thanks a lot folks.

pmohr

iTrader: (26)

Not easily. You could turn the AC on and put the steering at full lock, but the IACV will up the idle and likely make any minor misfires less apparent.

What I'd do it just test all of the coils.

Wait a second, you're a '99? On original coils?

Replace them. All.

AndrewR2442

iTrader: (1)

100% you have at least 1 or more failing coils. If you do end up taking it to a shop, make sure they tell you which specific coils need to be replaced.

Do not let them replace them for you. If you can change your spark plugs, then you already know how to replace the coil.

The ECU will only give you an error code if the misfire is bad enough. Coils are known to fail over a period of time and not at once.

Jessiblack

Engine RPM Fluctuation 1358. Rough Idle 1361. Stalling & Excessive Idle 1369.
.... Issues related to non-specific internal and external noise, squeaks and
odors. .... Uneven Pad Wear – Caliper Issue? 1424. Slotted/Vented Rotors 1427.
.... Fault Code P0401 - EGR System & Dual Exhaust Backpressure 1353.

DreamCatcher

Excellent info Pmohr, and AndrewR2442! I'll have the resistances checked of the injectors and coil packs at the mechanic tomorrow, and replace based on what is malfunctioning.

Thanks a lot!



Did you just do a search and are giving me potential codes? Please note that my ECU is not throwing out any code(s).

DreamCatcher

So I went to the mech today, and he checked the car. He says that one coil pack and all six spark plugs need to be replaced.

He quoted $350 for the repair, which includes the parts.

What do you folks think- is it reasonable? I mean, I checked around, and a coil pack costs about ~80 bucks, and spark plugs are about ~60 (six of them).

pmohr

iTrader: (26)

You can get plugs for ~$1 each (honestly I see no real point in going with the high priced plugs, all you get is longer life).

You should replace all of the coils, they're all going to die at some point; unless you want to be chasing them one by one, correct the problem now.

You could go with used coils from the classifieds, junkyard, or eBay. Or, go with new ones from eBay, online stores, or an auto parts store.

If you go used, make sure they aren't for a '99. Search around, you'll find threads about the lowest priced new coils.

DreamCatcher

I wanted to, but the mech scared me off by saying that six coil packs would run me $1000

Are those things really that expensive?

I will be looking around for used "new" coils, but was wondering if there would be such a huge difference in price...

Thanks for your reply, pmohr!

pmohr

iTrader: (26)

Of course he said that, he's probably talking dealer price plus his markup.

Check eBay, there's a used set on there for ~$140 shipped.

Absolutely no need to have a shop do this, you could do the entire job yourself quite easily with even the most basic of tool sets.

AndrewR2442

iTrader: (1)

http://www.trademotion.com/partlocat...layCatalogid=0

^ Nissan dealerships have really good online prices. ($79 + shipping)

Autozone aftermarket coils were ($75)

My local Nissan dealership listed hashins for ($100.24)

Rockauto.com has the cheapest prices I could find ($59 + shipping). But i ended up getting 2 outa 3 defective coils when i bought from them. On the other hand, they have great prices and good service. They did refund me minus the shipping.




Yes that mechanic was indeed trying to make a profit off of you when with out any discounts he can get the set for $600+tax straight from Nissan. Or for under $450+tax and/or shipping anywhere else. But if i was a mechanic, i'd be trying to do the same thing.

DreamCatcher

Hey folks, just wanted to let you know that I bought the coil packs and plugs from AutoZone (and a spark plug socket), I was able to read up and change my coil packs and plugs.

Now the car is back the way it used to be, its great!

I was mostly a theory guy, I like reading up to understand the mechanics of the vehicle, but I am always scared to screw around with my only vehicle that takes me to school and work.

Im glad I didn't blow up anything in the process haha.


Thanks a lot for all of your help! This is why I love the forums.